This isn’t a mark of degradation at all. “Back in the day” of non-monetization isn’t sustainable for any decent length of time because eventually the people donating (VCs) will want a return or will run out of money.
If they are raising prices (amount of ads shown) and people continue to pay then I can’t fault them for it.
As I type this I realize that both you and the person I was originally responding to are just expressing that you don’t like the price increases. Which is totally fair.
Of course they could, just make it part of the service agreement.
I would feel much inclined to pay for youtube if they filtered out all ad-funded content.
Even better, they could have a model where content creators for the paid service got their piece of the revenue based in quality metrics rather than quantity metrics.